/*
 *  Copyright (c) Iris Dev. team. All rights reserved.
 *  See http://www.communico.pro/license for details.
 *
 */
#ifndef _AS_CONSISTENT_HASH_HPP__
#define _AS_CONSISTENT_HASH_HPP__ 1

#include <ASTypes.hpp>
#include <STLString.hpp>
#include <STLVector.hpp>
//#include <STLAlgorithm.hpp>
#include <algorithm>
namespace CAS_MOD
{

/**
  @class ConsistentHash ConsistentHash.hpp <ConsistentHash.hpp>
  @brief Consistent hash implementation
*/
template <typename T>class ConsistentHash
{
public:
	enum State { OK = 0, ERROR = -1 };

	/**
	  @brief Constructor
	  @param iIElements - min. number of elements per one item
	*/
	ConsistentHash(const UINT_32 iIElements = 10);

	/**
	  @brief Add element to hash
	  @param sElementName - key name
	  @param oElement - element to add
	  @param dWeight - element weight
	  @return Element Id
	*/
	State AddElement(const STLW::string  & sElementName,
	                 const T             & oElement,
	                 const W_FLOAT         dWeight = 1.0,
	                 const bool            bEnabled = true);

	/**
	  @brief Remove Element by given name
	  @param sElementName - element name
	  @return 0 - if success, -1 - otherwise
	*/
	State RemoveElement(const STLW::string  & sElementName);

	/**
	  @brief Get Element by given name
	  @param sElementName - key name
	  @return Nearest element
	*/
	State GetElement(const STLW::string  & sElementName,
	                 T                   & oElement);

	/**
	  @brief Enable Element
	  @param sElementName - element name
	  @return OK - if success, ERROR - otherwise
	*/
	State EnableElement(const STLW::string  & sElementName);

	/**
	  @brief Disable Element
	  @param sElementName - element name
	  @return OK - if success, ERROR - otherwise
	*/
	State DisableElement(const STLW::string  & sElementName);
private:
	/**
	  @struct ElementRec ConsistentHash.hpp <ConsistentHash.hpp>
	  @brief Element record
	*/
	struct ElementRec
	{
		/** Element name                      */
		STLW::string    element_name;
		/** Element value                     */
		T               element;
		/** Element weight                    */
		W_FLOAT         weight;
		/** Flag, element enabled or disabled */
		bool            enabled;
	};

	/**
	  @struct ElementRec ConsistentHash.hpp <ConsistentHash.hpp>
	  @brief Continunum record
	*/
	struct ContinuumRec
	{
		/** Element position   */
		UINT_32       pos;
		/** Element hash value */
		UINT_32       hash;
	};

	/**
	  @brief Sorting functor
	*/
	struct ContinuumRecLess
	{
		bool operator()(const ContinuumRec  & oX,
		                const ContinuumRec  & oY) const
		{
			return oX.hash < oY.hash;
		}
	};

	/** Min number of elements per one item  */
	const UINT_32               iElements;
	/** List of elements                     */
	STLW::vector<ElementRec>    vElements;
	/** Continuum of elements                */
	STLW::vector<ContinuumRec>  vContinuum;
	/** CRC32 data                           */
	static UINT_32              aCRC32Tab[256];

	UINT_32 Hash(const STLW::string  & sElementName,
	             const UINT_32         iSeed = 0xFFFFFFFFUL) const;
};

template <typename T> UINT_32 ConsistentHash<T>::aCRC32Tab[] =
{
	0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
	0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
	0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
	0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
	0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
	0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
	0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
	0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
	0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
	0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
	0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
	0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
	0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
	0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
	0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
	0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
	0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
	0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
	0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
	0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
	0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
	0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
	0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
	0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
	0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
	0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
	0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
	0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
	0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
	0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
	0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
	0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
};

//
// Constructor
//
template <typename T> ConsistentHash<T>::ConsistentHash(const UINT_32 iIElements): iElements(iIElements) { ;; }

//
// Hash function
//
template <typename T> UINT_32 ConsistentHash<T>::Hash(const STLW::string  & sElementName,
                                                      const UINT_32         iSeed) const
{
	UINT_32 iCRC32 = iSeed;
	for (UINT_32 iPos = 0; iPos < sElementName.size(); ++iPos)
	{
		iCRC32 = aCRC32Tab[(iCRC32 ^ sElementName[iPos]) & 0xFF] ^ (iCRC32 >> 8);
	}

return (iCRC32 ^ iSeed);
}

//
// Add element to hash
//
template <typename T> typename ConsistentHash<T>::State
  ConsistentHash<T>::AddElement(const STLW::string  & sElementName,
                                const T             & oElement,
                                const W_FLOAT         dWeight,
                                const bool            bEnabled)
{
	// TBD: check duplicate name
	ElementRec oRec = { sElementName, oElement, dWeight, bEnabled };
	const UINT_32 iRecPos = vElements.size();
	vElements.push_back(oRec);

	UINT_32 iHash = 0xFFFFFFFFUL;
	const UINT_32 iPoints = iElements * dWeight;

	for (UINT_32 iPos = 0; iPos < iPoints; ++iPos)
	{
		// Calculate hash
		iHash = Hash(sElementName, iHash);

		ContinuumRec oContinuumRec = { iRecPos, iHash };
		vContinuum.push_back(oContinuumRec);
	}

	STLW::sort(vContinuum.begin(), vContinuum.end(), ContinuumRecLess());
return OK;
}

//
// Remove Element by given name
//
template <typename T> typename ConsistentHash<T>::State
  ConsistentHash<T>::RemoveElement(const STLW::string  & sElementName)
{
	bool bFound = false;
	STLW::vector<ElementRec> vTMP;
	typename STLW::vector<ElementRec>::iterator itvElements = vElements.begin();
	while(itvElements != vElements.end())
	{
		if (itvElements -> element_name == sElementName) { bFound = true; }
		else
		{
			vTMP.push_back(*itvElements);
		}
		++itvElements;
	}
	if (!bFound) { return ERROR; }

	vElements.erase();

	typename STLW::vector<ElementRec>::iterator itvTMP = vTMP.begin();
	while(itvTMP != vTMP.end())
	{
		AddElement(itvTMP -> element_name,
		           itvTMP -> element,
		           itvTMP -> weight,
		           itvTMP -> enabled);
		++itvTMP;
	}
return OK;
}

//
// Enable Element by given name
//
template <typename T> typename ConsistentHash<T>::State
  ConsistentHash<T>::EnableElement(const STLW::string  & sElementName)
{
	typename STLW::vector<ElementRec>::iterator itvElements = vElements.begin();
	while(itvElements != vElements.end())
	{
		if (itvElements -> element_name == sElementName)
		{
			itvElements -> enabled = true;
			return OK;
		}
		++itvElements;
	}

return ERROR;
}

//
// Disable Element by given name
//
template <typename T> typename ConsistentHash<T>::State
  ConsistentHash<T>::DisableElement(const STLW::string  & sElementName)
{
	typename STLW::vector<ElementRec>::iterator itvElements = vElements.begin();
	while(itvElements != vElements.end())
	{
		if (itvElements -> element_name == sElementName)
		{
			itvElements -> enabled = false;
			return OK;
		}
		++itvElements;
	}

return ERROR;
}

//
// Get element
//
template <typename T> typename ConsistentHash<T>::State
  ConsistentHash<T>::GetElement(const STLW::string  & sElementName,
                                T                   & oElement)
{
	if (vContinuum.empty()) { return ERROR; }

	// Calculate hash
	const UINT_32 iHash = Hash(sElementName);

	// Get nearest value from cintinuum
	INT_32 iLeft  = 0;
	INT_32 iRight = vContinuum.size();
	INT_32 iMid   = 0;
	for(;;)
	{
		iMid = (iRight + iLeft) >> 1;

		if (iMid == iLeft) { break; }

		if      (vContinuum[iMid].hash < iHash) { iLeft  = iMid; }
		else if (vContinuum[iMid].hash > iHash) { iRight = iMid; }
		else { break; }
	}

	iRight = vContinuum.size();

	INT_32 iPos = iMid;
	for (; iPos < iRight; ++iPos)
	{
		ElementRec & oRec = vElements[vContinuum[iPos].pos];
		if (oRec.enabled)
		{
			oElement = oRec.element;
			return OK;
		}
	}

	iPos = 0;
	for (; iPos < iMid; ++iPos)
	{
		ElementRec & oRec = vElements[vContinuum[iPos].pos];
		if (oRec.enabled)
		{
			oElement = oRec.element;
			return OK;
		}
	}

return ERROR;
}

} // namespace CAS_MOD
#endif // _AS_CONSISTENT_HASH_HPP__
// End.
